A neurological phenomenon in which an irritation in one sensory or cognitive system leads to an automatic, involuntary response in another sensory system. Another definition of synesthesia is a phenomenon of perception in which the stimulation of one sense organ (due to the irradiation of excitation from the nervous structures of one sensory system to another), along with sensations specific to it, causes sensations corresponding to another sense organ. It should be borne in mind that synesthesia is not a mental disorder.